Ichthyological ecoregions of Argentina Item Type monograph Authors López, Hugo Luis; Morgan, Cecilia C.; Montenegro, Marcelo J. Publisher División Zoología Vertebrados, Museo de La Plata. Download date 02/10/2021 08:19:22 Link to Item http://hdl.handle.net/1834/19453 ProBiota (Programa para el Estudio y Uso Sustentable de la Biota Austral) Directors Dr. Hugo L. López E-mail: [email protected] Dr. Jorge V. Crisci E-mail: [email protected] Dr. Juan A. Schnack E-mail: [email protected] Facultad de Ciencias Naturales y Museo - UNLP Paseo del Bosque s/n (1900) La Plata, Buenos Aires, Argentina Cover illustration taken from: Lahille, F., 1929. Una hora entre los pejerreyes, Tomo commemorativo del 25º Aniversario de la Fundación de la Facultad de Agronomía y Veterinaria, Universidad de Buenos Aires, 59 pp. Documents Serie, ProBiota, Electronic version, 2002. ISSN 1666-731X División Zoología Vertebrados, Museo de La Plata 1 ICHTHYOLOGICAL ECOREGIONS OF ARGENTINA(*) Hugo L. López1,2, Cecilia C. Morgan1 & Marcelo J. Montenegro1x 1 División Zoología Vertebrados, Museo de La Plata, Paseo del Bosque s/nº, 1900 La Plata, Argentina. ProBiota. 2 Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (CIC). 3 Instituto de Limnología “Dr. Raúl A. Ringuelet” (ILPLA), CONICET-UNLP. INTRODUCTION The Argentine Republic is situated in the southernmost portion of the American continent, occupying over 2,785,600 km2 not including the Antarctic territory. The country ranges from subtropical areas (21º46’S) to subantarctic regions (55º03’S), extending latitudinally over about 4,000 km. It possesses significant latitudinal and altitudinal variation (33º of latitudinal range, and heights from Bajo de San Julián in Santa Cruz province at 105 m below sea level, up to Mt. Aconcagua, 6,959 m over sea level), as well as two gradients of physical variability, extending in north-south and east-west directions. Owing to these features, the country presents a wide range of climates and soil types, being one of the countries with greatest diversity of biogeographical units (Lean et al., 1990, In: Bertonatti & Corcuera, 2000). There are four main hydrographic systems: Río de la Plata basin, the Atlantic and Pacific drainages, and several endorrheic systems. Within these basins, the ichthyofaunistic assemblage is well represented, with different magnitude in accordance with the different taxonomic groupings and regions considered. From an ichthyogeographic standpoint, and according to the works of Ringuelet (1975) and Arratia et al. (1983), Argentina is included in the Brasilic and Austral Subregions. The first of these is represented by two domains: the Andean Domain, comprising the southernmost portion of Titicaca Province, and the Paranensean Domain, including part of Alto Paraná and Paranoplatensean Provinces. The Austral Subregion is represented in Argentina by the Subandean-Cuyan and Patagonian Provinces. The present survey indicates that there are about 441 fish species in Argentina, distributed throughout the country; this number represents less than 10% of the total fish species occurring in the Neotropical Region. There is a recognizable trend of faunal impoverishment, both in North-South and East-West direction, reaching its maximum expression in the provinces of Tierra del Fuego (situated at approximately 52º30’S to 55ºS, and 65ºS to 68º50’W) and San Juan (approximately 28º50’S and 67ºW to 70º45’W), which have 4 and 5 fish species respectively. In north-south direction, one of the regional indicators of this phenomenon is the Salado river basin in Buenos Aires province, which constitutes the southern distributional boundary for the majority of the paranoplatensean ichthyofauna; 12 of the families occurring in the Paraná-Plata system are absent from this pauperized paranensean ichthyofaunal assemblage. Most of the continental fish fauna of Argentina belongs to the primary division of Myers (1949), while some elements are included in the secondary division and others in an amphibiotic or ‘marine penetration’ category. This ichthyofaunistic scope encompasses a wide range of morphological, biological, ecological and ethological types (benthic and . e-mail: [email protected] (*) This work was made as part of the project Freshwater Ecoregions of the World, Conservation Science Program, World Wildlife Fund, USA. A Spanish version of this document is in press by Comisión Administradora del Río Uruguay (CARU). 1 pelagic, migrating and sedentary, haematophagous or parasites, annual species, inhabitants of plains or heights, estivation-adapted, etc.) inhabiting different regions within the national territory. MATERIALS AND METHODS In this work we have adopted the ichthyogeographic proposals of Ringuelet (1975) and Arratia et al. (1983), which in general terms are coincidental with the Argentinian geographical regions, and the hydrographical scheme of Mazza (1961), excluding from our study the Pacific drainage basins. In addition to these, we referred to the works of Menni et al. (1996), Arratia (1997) and Dyer (2000). For background on the ichthyofaunistic composition of Argentina we considered López et al, (1987), and we consulted various sources such as Ringuelet et al. (1967), the bibliographical references in López et al. (1981, 1982, 1987, 1989, 1991, 1993, 1994) and Ferriz et al. (1998), as well as Malabarba et al. (1998) and various regional and reviewing works that are mentioned in Additional Bibliography. With respect to environmental protection and conservation, we considered the works of Chébez (1994), Bello and Úbeda (1998), Pascual et al. (1998), Bertonatti and Corcuera (2000) and López (2001). For the delineation of the ecoregions (figure 1) we performed a similarity analysis of the previously delineated hydrographical basins, using all the documented records of fish species as characters (Table 1). Table 2 shows the fish families present in each basin as well as their total number. The exotic fish species present in Argentina (Table 3) were not included in the analysis, and neither were some native species which have been spread by anthropogenic action (namely, Odontesthes bonariensis, Jenynsia multidentata and Cnesterodon decemmaculatus). The records that appeared doubtful as to the identification of the species or localities were also dismissed. The similarity analysis was performed applying Jaccard association coefficient and UPGMA clustering with NT-SYS program to obtain the resulting phenogram. The outcome of this analysis, along with other considered elements such as distinctive features of the systems’ dynamics, ecological determinants, and processes of environmental degradation occurring in each of the considered areas, were the basic elements used in the delineation of ecoregions. In the discussion of each ecoregion we have included the number of fish species for each basin, and the percentage that each represents in the total 441 species considered for the analysis (Table 1) is indicated in parentheses. In the last part of the characterization of each ecoregion we indicate the corresponding category in the classification of wetlands of Argentina (Canevari et al., 1998), the ecoregions of Argentina as delineated by Burkart et al. (1999) and the zoogeographical regions of Ringuelet (1961). In the cases where we have tentatively extended the ecoregions into neighboring countries, the description of the ecoregion and all numerical data (including surface area) correspond exclusively to the Argentinian portion. With respect to the bibliographical references, we have listed separately the works mentioned within the text from the additional bibliography. RESULTS 1) MISIONERAN ECOREGION Limits The ecoregion is limited to the N by Iguazú river; to the W by Paraná river; to the E, by Uruguay river; to the SE it abuts on Lower Uruguay River ecoregion; to the SW, by the courses of two creeks, Itaembé creek (tributary of Paraná river) and Chimiray creek (tributary of Uruguay river), both included in this ecoregion, and by means of an imaginary line running between their headwaters. We have extended tentatively this ecoregion outside Argentinian territory to encompass neighboring areas in Brazil and Paraguay which are drained by tributaries of Paraná and 2 Uruguay rivers. Description According to Popolizio (1972) it’s a plateau with “subhorizontal tabuliform structure”, with a dorsal ridge formed by the orographic systems of San José, del Imán or Itacuara and the Misiones sierras. The fluvial system arises from this mountainous ridge and its spurs, and the streams descend on either side of the mountains to flow into Paraná and Iguazú rivers (western slope) and Uruguay river (eastern slope). These courses present many waterfalls originated in by basaltic rock exposures, and among these, the outstanding Iguazú Falls, falling in an arc of approximately 2,700 m of which 2,100 are within Argentina and 600 m correspond to Brazil. Surface area: 29,801 km2 (all of Misiones province) Main basins: rivers Iguazú, Paraná and Uruguay, which form the natural boundaries of Misiones province, along with an important interior hydrographic network; some streams belonging to the Paraná river basin are Uruguaí or Marambas, Piray-Guazú, Cuñapirú, and Yabebyrí creeks, and some from Uruguay basin are Pepirí-Guazú and Yaboty rivers, and Persiguero and Chimiray creeks. Terrestrial habitats The rainforest’s floristic richness goes unparalleled in Argentina. The contrast between the greens of the forest and the